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The Pati–Salam model states that the gauge group is either SU(4) × SU(2)L × SU(2)R or (SU(4) × SU(2)L × SU(2)R)/Z2 and the fermions form three families, each consisting of the representations(4, 2, 1) and (4, 1, 2). This needs some explanation. The center of SU(4) × SU(2)L × SU(2)R is Z4 × Z2L × Z2R. The Z2 in the quotient refers to the two element subgroup generated by the element of the center corresponding to the two element of Z4 and the 1 elements of Z2L and Z2R. This includes the right-handed neutrino, which is now likely believed to exist. See neutrino oscillations. There is also a (4, 1, 2) and/or a (4, 1, 2)scalar field called the Higgs field which acquires a VEV. This results in a spontaneous symmetry breaking from SU(4) × SU(2)L × SU(2)R to SU(3) × SU(2) × U(1)Y)/Z3 or from (SU(4) × SU(2)L × SU(2)R)/Z2 to (SU(3) × SU(2) × U(1)Y)/Z6 and also,

As mentioned above, both the Pati–Salam and Georgi–Glashow SU(5) unification models can be embedded in a SO(10) unification. The difference between the two models then lies in the way that the SO(10) symmetry is broken, generating different particles that may or may not be important at low scales and accessible by current experiments. If we look at the individual models, the most important difference is in the origin of the weak hypercharge. In the SU(5) model by itself there is no left-right symmetry (although there could be one in a larger unification in which the model is embedded), and the weak hypercharge is treated separately from the color charge. In the Pati–Salam model, part of the weak hypercharge (often called U(1)B-L) starts being unified with the color charge in the SU(4)C group, while the other part of the weak hypercharge is in the SU(2)R. When those two groups break then the two parts together eventually unify into the usual weak hypercharge U(1)Y.